Application of Plants as Bio-markers to Assess Wetland Ecosystem Health
- Atomic Energy of Canada Limited, Chalk River Laboratories, Chalk River, Ontario K0J 1P0 (Canada)
Exposure of non-human biota to radionuclides or other contaminants depends upon a number of factors, which relate to the distribution of a given contaminant in the environment relative to the utilization of the environment by resident biota. Potential effects to biota following contaminant exposure must then be assessed based on the development of defensible linkages between the probability of exposure and the probability of corresponding effects. In many cases, contaminants, such as radionuclides, can show highly localized distributions in natural systems, covering relatively small spatial extents. Despite this, however, in the case of sedentary organisms, such as plants, it is possible for individuals to live in areas with relatively high contaminant levels throughout their lives. Plants represent integral components of ecosystems due to their capacity to use solar energy to convert CO{sub 2} into digestible organic molecules, due to their position at the base of terrestrial and aquatic food chains, and due to their importance as habitat and refuges for terrestrial and aquatic biota. As a result, the integrity of ecosystems is dependent upon plant health. The objective of this study was to determine whether significant changes in parameters reflecting plant photosynthetic capacity occurred with significant differences in {sup 14}C exposure in a wetland ecosystem. The study was conducted in Duke Swamp, a wetland ecosystem that receives {sup 14}C through groundwater influx. Sampling was conducted at 4 locations with varying {sup 14}C concentrations. These locations were selected based on a detailed survey of the swamp that was conducted in 2001 to evaluate the spatial distribution of {sup 14}C in surface vegetation, relative to concentrations reported in Sphagnum moss and soil in the swamp in the early 1990's. Locations were also selected to assess the impacts of both {sup 14}C exposure and the degree of incident solar radiation on plant photosynthetic parameters. A screening analysis of resident plant species in Duke Swamp was conducted and alder was ultimately selected as the test species due to its propensity to accumulate {sup 14}C in leaf tissues and its ubiquitous distribution throughout Duke Swamp, as well as in wetlands, in general. Carbon-14 concentrations in alder leaves and the net photosynthetic rate in leaf tissues were then measured at each study site throughout the summer of 2004. In general, {sup 14}C concentrations in Duke Swamp surface vegetation have declined between 1991 and the present by approximately 2- to 3-fold in the area of the swamp with the highest {sup 14}C concentrations, with a corresponding 34% reduction in the spatial extent of these areas. Carbon-14 specific activities in alder leaf tissues collected in the 2004 study ranged from 0.280 Bq/g C at Site 24 to 14.3 Bq/g C at Site 35, with intermediate values of 1.21 and 2.60 Bq/g C detectable in leaves collected at Sites 9 and 56, respectively. Comparison of {sup 14}C levels in alder leaves with the net rate of photosynthesis showed that no significant relationships existed between {sup 14}C exposure and the photosynthetic capacity of alders, despite the 4.1- to 51-fold differences in alder {sup 14}C specific activities between sampling locations. In fact, one-way analysis of variance (ANOVA) indicated that the net rate of photosynthesis in alder leaves was significantly higher at Site 35 (the site with the highest {sup 14}C concentrations) than at either Site 24 (the site with the lowest {sup 14}C concentrations) or Site 9 (the site with the second lowest {sup 14}C concentrations). By comparison, alder leaves collected at Site 56 showed no significant difference in net photosynthesis in comparison to values measured in leaves collected at Site 35. Based on these data, it is likely that light availability was a dominant factor influencing the photosynthetic capacities of alders in Duke Swamp, since both Site 56 and Site 35 were located in shaded areas, whereas Sites 9 and 24 were situated in open areas with relatively high light penetration. This was further supported by literature data, which indicated that the rates of photosynthesis measured in alder leaves collected in Duke Swamp fell within the same range as those measured for other temperate, deciduous tree species that presumably were not being exposed to elevated {sup 14}C concentrations. It is important to note that although it was possible to compare net photosynthetic rates at shaded locations showing high versus low {sup 14}C concentrations, it was not possible to assess the plant photosynthetic capacity at sunny versus shaded locations in areas with high {sup 14}C levels due to the small, localized nature of the {sup 14}C plume in the swamp, which represented only approximately 0.00015 km{sup 2} and fell entirely in a shaded area.
- Research Organization:
- American Nuclear Society, 555 North Kensington Avenue, La Grange Park, Illinois 60526 (United States)
- OSTI ID:
- 21144182
- Resource Relation:
- Conference: DD and R 2007: ANS Topical Meeting on Decommissioning, Decontamination, and Reutilization 2007, Chattanooga, TN (United States), 16-19 Sep 2007; Other Information: Country of input: France; 3 refs; Related Information: In: Proceedings of the 2007 ANS Topical Meeting on Decommissioning, Decontamination, and Reutilization - DD and R 2007, 336 pages.
- Country of Publication:
- United States
- Language:
- English
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